Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
  • B23H1/10—Supply or regeneration of working media
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
  • B23H1/02—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges
  • B23H1/022—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges for shaping the discharge pulse train
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
  • B23H1/02—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges

Definitions

• the present invention is directed to a method for electric discharge machining of an electric discharge machine using a conductive machining fluid.
• FIG. 3 is a circuit diagram showing a power supply for machining by a conventional electric discharge machining method disclosed in, for example, Japanese Patent Application Publication No. 60-85882 '.
• (1) is the machining electrode
• (2> is the workpiece
• (3> is the second DC power source
• M are power transistors
• Transistor (4 (current limiting resistor connected to the emitter side of 261;
• 9 ) detects the occurrence of discharge between the electrode (1) and the pole formed by the workpiece f2>)
• Discharge detection means ( ⁇ is switching means, (1.
• a power transistor is a power transistor
• a second drive circuit for driving is diodes to prevent reverse flow of current
• (18 ) Is the first drive circuit that drives the transistor ffl, and is the first DC power supply
• the switching means (12) is the first and second drive circuit ( 13, and (18) are controlled.
• the ambient dance Rgap is represented by the following equation as shown in FIG.
• Vgopen ⁇ ⁇ "', _ ⁇ ⁇ E (2)" Rgap 4-R.
• Vgopen used here is called the no-load voltage.
• the voltage between the electrodes after discharge is the arc voltage Vgarc.
• the total current supplied from the power supply is I
• the no-load voltage is applied to the electrolytic current flowing according to Ohm's law with respect to the impedance between gaps Rgap.
• 3 ⁇ 4 ⁇ I £ open ⁇ of the current, 3 ⁇ 4 "I ⁇ arc during the discharge, and the discharge current flowing by the discharge phenomenon is Id.
• Fig. 9 shows the circuit of the power supply for electrical discharge machining. In the figure, two sets of current circuits are connected in parallel to the electrodes (11 and the workpiece 1) . , Actual machining current
• discharge current is driven by the second drive circuit 131.
• the power transistor 1 and the second DC power supply are supplied from a circuit consisting of a current limiting resistor 1 and a diode.
• a power transistor (26), a current limiting resistor 25), a diode (15), and a first DC Power source (From the circuit consisting of 19, more current flows between the electrode (1) and the workpiece. That is, more current flows than during discharging.) 3, The voltage between the poles is increased when no load is applied, so that discharge is easily induced.After the discharge occurs between the poles, the discharge is detected by the discharge detection means [ 9] , and the switching means is switched on. By sending a signal to the first drive circuit and turning off the power transistor, D, the discharge current is supplied only from the second DC row source).
• the resistance value RM of the resistor is a value for obtaining the discharge current corresponding to the desired surface roughness and machining speed
• the resistance value Rs of the resistor (25) is sufficient for starting the discharge together with the RAf side.
• E 2 DC power supply voltage on the second drive circuit side.
• the conventional EDM method uses the method of switching the internal impedance of the power supply as described above.
• the internal impedance of the power supply it is necessary to obtain the value of the gap impedance Rgap.
• the electrode (1) and the workpiece are not necessarily opposed to each other on a plane, and the distance between the electrodes cannot be directly substituted for in (1).
• the specific resistance of the conductive machining fluid changes with the progress of machining, and as shown in Fig. 12, it has different values between the machining fluid tank, the power supply, and the discharge gap. It is difficult to measure the specific resistance between discharge gaps. From the above points, it is difficult to calculate the impedance Rgap between the poles by measuring the distance between the poles, the facing area S between the poles, and the specific resistance of the machining fluid. It will change. In addition, if the internal impedance value of the power supply is not corrected for the gap impedance Rgap that changes with the progress of the addition, the following problems will occur.
• the present invention has been made to solve the above-mentioned problems, and stabilizes machining over the entire electric discharge machining, and automatically changes and sets the internal impedance of the power supply.
• a constant surface roughness is maintained from time to time with respect to changes in the distance between the poles, the facing area S between the poles, and the change in the impedance between the poles, Rgap, due to the change in specific resistance.
• the impedance between the electrodes is detected, and the internal impedance of the power supply for obtaining a desired no-load voltage and the desired discharge current are determined based on the data. It is designed to calculate the internal impedance of the power supply to obtain it and to set this on the power supply circuit for electric discharge machining.
• the electric discharge machining method according to the present invention is based on the data of the detected impedance between the poles. ⁇ Calculate the internal impedance value of the power supply that supplies the voltage, and control the internal impedance value of the power supply so that the desired additional current flows after the occurrence of discharge.
• Fig. 1 is a circuit diagram of a power supply for machining in the method of electric discharge machining according to the present invention
• Figs. 2 to 5 are circuit diagrams of a power supply for machining in another method of the present invention.
• Fig. 6 is a waveform diagram of the inter-electrode voltage and inter-electrode current
• -Fig. -.0.7 ⁇ shows the correlation between arc voltage and discharge current
• Fig. 8 is the latest data of the inter-electrode impedance.
• Fig. 9 is a circuit diagram of a power supply for machining in the conventional EDM method.
• Fig. 10 is a diagram of the gap between electrodes when a conductive machining fluid is used.
• Fig. 11 is a diagram showing the increase of the opposing area as the machining of an electrode with a complicated shape proceeds
• Fig. 12 is a diagram for explaining the difference in the specific resistance of the machining fluid.
• (1) is a working electrode
• (2) is a workpiece
• (3) is a DC power supply for machining
• ) is a power transistor group consisting of (4-1), (4-2) ⁇ -C4-n), and is C5-1), (5-2) ......... (5 ⁇ n) force, the current limiting resistors connected to the emitter side of the power transistors (4-1), C 4-2)... (4 ⁇ n), respectively.
• (6) and & 5) die O over de for preventing reverse flow of current, the detection ⁇ flow power, (8> the resistance for limiting the current from the detection ⁇ flow power), (the machining gap To detect that a discharge can occur;
• CL01 is a detecting means for detecting the gap impedance Rgap, and is a detecting means (the gap impedance detected by »
• the impedance between the poles; Bgap (calculation means for calculating the internal impedance of a suitable power supply; (12) indicates the power based on the calculation result of the calculation means
• a switching means for determining the ON / OFF combination pattern of the transistor groups ( ⁇ , ie, the switching output, and for temporarily storing a plurality of these patterns, a is a power transistor group
• (14) is storage means for storing the internal impedance value of the power supply calculated by the calculation means
• ⁇ is The resistance in the current limiting resistor group si and the power transistor connected thereto are selected, and the decoding means for selecting the combination pattern are the discharge detection means (switching the signal from the 91
• the oscillator sent to (12), (18 is the code (11 ), (12), 14), M), CL7) power control circuit
• (L9I is the current limiting resistor (8) is a voltage divider that divides the voltage between contacts.
• the detection means (10) directly measures the gap impedance Rgap by the method described below. According to these methods, (because the impedance between gaps, Rgap, can be measured directly without depending on the gap distance, the facing area between poles, S, and the specific resistance of the machining fluid in Eq. 11, Such problems can be solved.
• the first method is as follows. That is, during the downtime of the DC power supply for machining (), a detection voltage of the same polarity as that of the DC power supply for machining ( 3 ) is applied between the poles by another DC power supply for detection m. This method calculates the gap impedance Rgap from the voltage that appears between the gaps.
• a DC power supply for detection ( 7) is provided and connected between the poles via a current limiting resistor.
• detection cannot be performed if a discharge occurs between the electrodes, so the voltage Vga between the electrodes must be set so as not to exceed the arc voltage.
• the detection DC power supply is set lower than the power supply voltage Va 3 ⁇ 4 arc voltage Vgarc, control becomes easier.
• Va> Vga rc as shown in Fig.
• the voltage Vgap detected by the detection means (10) is processed by the arithmetic means dl) for one time, and the limiting resistance ( 8 ) The value of is detected by the detection resistance switching circuit (19).
• the power supply voltage can be set lower than the arc voltage Vgarc.
• the limiting resistance to the optimum value, the detection accuracy of the voltage Vgap detected by the detecting means can be improved.
• Vga RgapVa
• a voltage is applied between the poles by machining and the power supply), and the gap impedance E Vgopen force during the no-load time until discharge occurs is calculated from the gap impedance: Rgap. I'll. That is, assuming that the internal impedance of the power supply when no-load voltage is applied is Rx, the following relationship exists between the power supply voltage E, the gap voltage Vgopen, and the gap impedance Rgap.
• E-V gopen is calculated. Note that there is a method of reading the above gap voltage Vgopen into the detection means as a digital value via an A) converter.
• This method has the major advantage that a DC power supply Va for detecting the gap impedance Rgap and a current limiting resistor Ra ( 8 >) are not required.
• Rga ⁇ ⁇ ⁇ - Rz ⁇
• ⁇ It can be calculated as Vgz.
• This method has the great advantage that the DC voltage mva for detecting the pole impedance Rgap and the current limiting resistor (Si Ra is not required. Also, the pole gap Vgz is detected during the idle time. Since the inter-impedance Rgap is calculated, discharge can occur immediately after the voltage is applied and the inter-electrode impedance Rgap can be calculated even when there is no load time, as in the second method described above.
• the following method can be used to determine the gap impedance Rgap.
• the processing power source has the same polarity as that of the processing power source) by another detection power source m, which has a lower E value than the arc voltage E Vgarc.
• a voltage is applied to the poles and the impedance between the gaps is calculated from the voltage that appears between the poles.
• This method is characterized in that the current limiting resistor of the DC power supply for detection is used and the current limiting resistor group [5i] of the machining power supply is used13. Compared to method 1, it has the great advantage that the current limiting resistor of the DC power supply for detection is not required.
• Iopeak force An appropriate value that does not roughen the machined surface.
• the internal impedance Rx of the power supply is calculated by the formula [9] from the target non-corrosion charge Vgopen and the measured inter-pole impedance Rgap.
• the electrolytic current I arc that does not contribute to machining changes according to the change in the gap impedance Rgap, so that the discharge current I required for machining is controlled constant.
• the I d and the electrolytic current I ar c. controls Ji iS the total current ⁇ in Gokumai down Pidan scan Rgap plus.
• Rgap Can be calculated.
• the internal bias values Rx and Ry of the power source calculated by the execution means M are sent to the storage means C14).
• the gap voltage is converted to the arc voltage during the pause time.
• the power supply internal impedance value Rz set to be below is also sent to the storage means M.
• the configuration is determined at the power supply design stage, but the decoding means uses any combination of resistors from the current limit 'resistance group ( 5 ) to realize the internal impedance of Rx, Ry, and Rz. Is determined, the part transistor connected to the resistor determined to be used is selected, and a combination pattern of the part transistors is created. As an example,
• Ry may be replaced with Ry instead of Rx.
• Ri and R2 3 ⁇ 4i are the current limiting resistors (5-1), respectively.
• the target no-load voltage E Vgopen requires at least the arc voltage Vgarc, but any voltage higher than that can be used in principle.
• the target value of the no-load voltage Vgopen there are two types of control: one is to match the target value, and the other is to not lower the target value if the target value can be easily obtained.
• the latter case occurs when the electrode area S is small and the inter-electrode impedance R gap is sufficiently large.
• the discharge detection by the discharge detection means is generally performed by comparing the discharge reference voltage with the voltage between the electrodes, the height of the no-load voltage depends on the time delay of the discharge detection. For this reason, the no-load voltage is as high as possible! ) It is better to keep it constant, and it is preferable to control it by means of a dip unit (111) so as to keep the no-load voltage constant.
• the gap impedance Rgap can be calculated by the detection means, and the calculated data can be output once for each pulse.
• the calculating means ⁇ calculates the internal impedance of the power supply based on the inter-pole impedance Rgap applied once for each voltage pulse by the detecting means.
• the first method is to calculate the internal impedance at the next noise and response from the gap impedance Rgap force output once for each pulse. In other words, this method attempts to use the information on the impedance between the poles at the time of the previous pulse to determine the internal impedance when the current pulse is loaded. It can respond to
• the second method is to use the latest n data among the data of the gap impedance R gap.
• n is performed to determine the average value Rgap-m, and the internal impedance of the power supply is calculated based on this value.
• the following third method can be considered using the memory described in the second method. This is a method in which the maximum Rgap among the latest n inter-pole impedances Rgap stored in memory is used as a representative value.
• the driving circuit ⁇ of the power transistor group # 1 decodes the data of the selection combination pattern of the power transistors sent from the switching means 12), and outputs the signal connected to the base of the corresponding power transistor. Power tiger on wire Outputs a signal to turn on the transistor.
• the internal impedance of the power supply is changed according to the following situations in each voltage pulse in response to the change in the impedance between gaps Rgap.
• the inter-pole impedance is detected in response to the change in the inter-pole impedance caused by the change in the discharge state between the poles, and the data is obtained based on the data. Since the internal impedance of the power supply is calculated, the optimal no-load voltage and the desired machining current can be obtained. Therefore, while maintaining a stable machining state, not only is it possible to obtain an EDM surface with a uniform surface roughness that is uniquely determined by the setting of machining conditions, but also large-area machining and finish machining that were previously impossible. D, inexpensive and practical An electric discharge machining method can be obtained, and an extremely effective effect is achieved.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

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• 1986
  • 1986-11-14 JP JP61271061A patent/JPS63123607A/ja active Granted
• 1987
  • 1987-11-10 US US07/231,820 patent/US4945199A/en not_active Expired - Fee Related
  • 1987-11-10 KR KR1019880700510A patent/KR910003052B1/ko not_active Expired
  • 1987-11-10 DE DE19873790717 patent/DE3790717T/de active Pending
  • 1987-11-10 WO PCT/JP1987/000868 patent/WO1988003453A1/ja active Application Filing
  • 1987-11-10 CH CH2798/88A patent/CH673609A5/de not_active IP Right Cessation
  • 1987-11-10 DE DE3790717A patent/DE3790717C2/de not_active Expired - Fee Related

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